Fibrous tobacco smoke filter containing finely divided solids



June 14, 1960 G. P. TOUEY FIBROUS TOBACCO SMOKE FILTER CONTAINING FINELYDIVIDED SOLIDS Filed Feb. 8, 1956 F/LAMENTS l/VSOLUBLE PHOSPHATE 0RCARBONATE 0F CIGARETTE WRAPPER George To uey I N V EN TOR.

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ATTORNEXS' United States Patent FIBROUS TOBACCO SMOKE FILTER CONTAININGFINELY DIVIDED SOLIDS George P. Touey, Kingsport, Tenm, asslgnor toKodak Company, Rochester, N.Y., a corporation of New Jersey Filed Feb.8, 1956, Ser- No. 564,172

Claims. (CL 131-208) The present invention relates to tobacco smokefiltering material and elements thereof suitable for use in cigarettes,pipes, cigarette holders, and cigar holders. In connection with theconsideration of the features described herein of spraying plasticizerin droplet form onto the continuous filaments and certain other details,reference may be made to Crawford and Stevens Patents 2,794,480 and2,794,239.

In the aforementioned patents, newly discovered advantages of a certaintype of fibrous tobacco smoke filter are discussed. The filter thereindescribed is prepared from a specially conditioned tow of syntheticallyspun, crimped continuous filaments and comprises a structurally unitary,elongated rod-like mass of filaments and an annular wrapper encirclingthe mass, each filament of the mass being substantially coextensivetherewith, the filaments being, in the aggregate, substantially parallelto each other and to the longitudinal axis of the mass with at least alarge number of the individual filaments having a plurality of shortportions thereof crimped into diverging and converging relationship tothe main filament axis, a plurality of the filaments having surfacesolvation bonds to contiguous filaments at random points of contact.Very good results have been obtained in the use of such filters for theremoval of nicotine and tars from tobacco smoke, especially in view ofthe fact that the filters supply other requirements, such as a unitarynature, rigidity, and resiliency, which are equally as necessary to thesuccess of a tobacco smoke filter.

.These filters also have a marked processing advantage over otherfilters known in the art. However, since the filaments in such filtersare generally parallel to each other, some channeling of the smokethrough the filter may be possible.

In other words, while a desirable amount of interference with the smoothflow of combustion products through the channels is provided by therandom bonds between adjacent filaments, by the incompleteness offilament orientation, and by the short filament portions which arecrimped into diverging and converging relationship to .the main filamentaxis, yet a limited amount of the smoke passing through the filterapparently travels through channels in a smooth, non-turbulent andundisturbed manner and thereby may be exposed to somewhat less than atheoretically maximum amount of impingement upon and contact with thesolid surfaces of the filter. Experimental investigations have shownthat any attempt to reduce the size or change the shape of thedetrimentally smooth smoke channels through the filters by an increasein filter density either through greater compaction of the filament massor through the use of finer filaments generally also results in anintolerable increase in pressure drop through the filter. It is alsounsatisfactory to substantially increase the amount of filament crimp inorder to obtain an increase in the amount of smoke impinge- 2 ment byincreasing the number of divergent and convergent filament portions.Additional crimp may weaken the filaments to the extent that they willnot be able to withstand the tension which is applied to obtain towbonding according to the Crawford and Stevens method.

In my copending US. patent application Ser. No. 413,- 950 filed March 3,1954, now Patent No. 2,881,769, of which the present application is acontinuation in part, I have disclosed and claimed an improvement basedon my discovery that the efficiency of filters of the type describedabove may be substantially increased without the expected equivalentincrease in pressure drop through the filters by preparing the filterswith deposits of finely divided solid vegetable starch particles in thesmoke channels provided by the spacing of adjacent filaments. The starchparticles are carried by and supported on the surfaces of the filamentsor fibers.

I have now discovered that a novel additive comprising one of certaininorganic salts provides a filtration efliciency equally as high as thestarches and exhibits an advantageous distinction in that it is capableof neutralizing gaseous acids, e.g. acetic acid, contained in the smokeand of serving as a buifering material for maintaining the pH of thesmoke in the desired range, i.e. the range of 6.5 to 7.5. I have furtherfound that these salts may be applied as finely divided solids from aslurry in a substantially non-volatile liquid plasticizer for thefilament material.

This invention, therefore, has as one object the production of anefficient cigarette smoke filter consisting of a filamentary filteringmaterial, particularly a material comprising an elongated,cylindricalbundle of substantially parallel and longitudinally alignedtextile fibers infused with finely divided particles of certaininorganic salts. Another object is to provide means for increasing theefiiciency of a cigarette filter prepared from a textile fiber. A stillfurther object is provision of a filter which is capable of removingnicotine, tars, and other deleterious components of cigarette smokewithout causing the smoke to be dry or distasteful. Another object is toincrease the efiiciency of tobacco smoke filters of the Crawford andStevens patents without creating a high pressure drop. A further objectis to provide a filter which not only removes particulate liquids andsolids from the smoke but also buifers the pH of the smoke. Stillanother object is to provide a firmly adhering particulate additive forfibrous tobacco smoke filters, particularly those filamentary filtersprepared with filaments bonded through a coalescence obtained by meansof the application of a spray of a liquid, solvent-type plasticizer. Afurther object is to provide a method of applying a powdered additive toa fibrous filter through the medium of a spray of a slurry of theadditive inn liquid plasticizer. Other objects will be obvious from thepresent specification and claims.

In accordance with the present invention, the fibers of a perviousfibrous filter mass are made to carry a dispersed deposit of a finelydivided, solid, inorganic salt selected from the group consisting of thephosphates and carbonates of magnesium and calcium. Accordingly, thepresent invention consists, in general, in a fibrous tobacco smokefiltering medium comprising a mass of fibers, the spacing of the fibersproviding minute passages for smoke through the mass, the mass carryingtherein an additive comprising finely divided solid particles of awater-insoluble inorganic salt of the type described above in an amountof about 5% to about 60% by weight of the fibers plus additive (theconcentration not being critical so long as there is suflicient additivepresent to improve the filtration efiiciency of the filter withoutcreating excessive Patented June 14, 1960- a acidsand carbonic acid.

' itr rs V ama s i J 4."

pressure drop); said particles being supported along the surfaces of andby the fibers and occupying positions along-the walls of and partiallyblocking said passages whereby a substantial portion of the smoke isimpinged on the particles.

' A more specific and very advantageous; embodimentoi' the inventioncomprises anew tobacco smoke filtering material of synthetically spuncontinuous crimped.thermo-- plastic filaments and an element madetherefrom, the ele-..

. ment comprising a structurally unitary elongated Cylin' 'dricalred-like, mass. of. filaments and an. annular wrapper encircling themass, ea h filament of the mass being substantially coextensive.therewith, the filaments inthe. agaregate eing. n substantial. paralleleac other nd withh -longitudinal. axis ofthe mass bu atleast a-pluralityof thefil'aments ea h ha ing e rality of shortfnortions. crimpedjinto,diverging and. con verging: relationship. to. the. mainfilamentjaxisl a'plurality of he filam nts. having; surface. solvation.b nds. to. con.- isu s' filam n fat random pointeot contact,- the. massarry ng u f rmly di perse therein anj dditive in the amount of' about 5%to about 6.0%.. by weight of the. massplus additive, the additive being.awateninsoluble salt selected from. the group consisting of mag-J u s mnd; c lci m s lts of orth meta-and pyro-phos "Mostadvantageously, theinventioncomprises a filter of cellulese acetate fibers havingsurfacesolvation bonds" achieyedthrough the application; of aplasticizer spray, the filter carrying uniformly dispersedwater-insoluble inorganic salt particles in the amount of about 5 toweight ofjthefilter. 7 I

"Any suitable means known to the art for spreadinga powder. onto. afibrous surface or through a fibrous mass may beemployed in preparingfilters of. the invention. Thus, for eitample, the inorganic'salt powdercan be blown onto the fibers, or it. can. beapplied. as. a slurry inwater" or in a volatile organic. vehicle. Another method is .to" applythe powder to the fibers electros' tatically,.i ;e. toinduce acharge. onthe fibers by friction oeother suitable means and then to runthefibersthrough archfiinber containing a. highly concentrated cloud of salt dustPreferably this is, done withthefibers or fila-' ments inthe form of atow :and in. a banded, i.e. spread-: o'titconditionJ Still. anothermethod for applying the salt particles is to. wet the surface of: thefilaments with an adhesive or a 'plasticizer before. exposing them to asolids dusting-deizice or other solidsapplicator. The

7 powder. then may. becoutinuously applied to an opened.

atonement mo in ow forme asdescribed in the Crawfor andstevenspatentsfThatis to say, tow from.

as ugly. roll. i one dto. e undleize-thefilaments and proyide 'a largerand t ere uniform tow cross section, 3. he? pened. tow is Spreaduniformly to. a, much.

larger width of e..g., lQ'times its original width, thereby.

Qutfofj fibrousfilterrnasses. generally areinore firmly boun ilappliedinja plasticizerslurry- Also,.by useof gfor; app ica ont f. he olid. ithasbeen possible ,the fiberswith larger; concentrationsof uniformlyedand-firmly bound additiye- Employment vof. a.

diluent inertto the powderandto the fiber is. valuable.

in ifacilitating applicationof larger quantities of. additive:

nlastie ae I The invention is illustrated in the accompanying drawingsin which: a r 1 a Fig. 1 represents a magnified View of the interior ofa mass of filtering material prepared in accordance with the invention,7 r

Fig. 2 is a view of a cigarette having attached thereto a tip preparedfrom a filtering material of the invention,

and a Fig. 3 represents aconsiderably magnified view of a section offilaments, such "as alsection of. mamentsnen migrate. into the'surfaoe.of the filaments or o herwise soften on the. surface of'thefil'amentss0. thlatthe.

' powdered additive of thepresentinyention is afiixed to the surface ofthe filaments at that point." Also, where plas ticizer droplets contact.adiacentI filaments, and crossing filaments, as illustratedfatll, .12and 13', because of'ithe softening. action of the plasticizerthefilaments will bond to. one another at random points.

: EXAMPLE 1..-MAGNE SIUM; CARBONATE A partially opened tow ofi-a Ycrirnpedi regular cross section cellulose acetate yarn. (39.2% acetyl)"having abont eight crimps pet-inch and containing approximately 10,000filaments of 8 denier per filament was slowly pulled. over a'compressedair bending device as disclosed in the. aforementioned Crawford andStevens patents and in Jackson, ULS; Patent 2,73'7,68'8, which spreadout'the filaments to a width of abouttwelve inches. While the tow was inthis spreadcondition it was sprayed using a conventional point spraygun) uniformly with finely-divided droplets of di(rnethoxyethyl)phthalate V plasticizer in order to make numerous portions'of the surfaces of the filaments soft andtacky; The spread tow 'was then passedthrough a dusting chamber which dusted the fibers uniformly with afinely divided (325 mesh) powder of magnesium carbonate (MgCOQ of a typecommercially available from Baker Chemical Co. and designated asanalytical grade. On. leaving thedusting chamber the. tow" contained 14%plasticizer and 18% magnesium carbonate, based on the total weight oftow; V carbonate and pla'sti'cizerl After. this spreading; spray ing,and. dusting, the treated tow was pulled baclc to its original shape ofa compact-f bundle, i.e. cord, and fed into a conventional cigarettefilter plug makingmachine which formed if'cylindrioally, Wrapped it withpaper, and cut it intorods- 78 in length and 7.5 mm. in diameter.: The:rods were then given a heat treatment for. one hour atz80f C. to cause.partial solvation: of the. acetate filaments: by theplasticizer'andtherebybond the carbona e parti les to the-filaments: andthefilamentsto each; other, imparting firmness to the--rods. Thereupon;

therodswere readily cut; into. 13. filter tip.lengths.v

ard, brand. available on.the retailrnarket-inthe U.S., The

"cigarettes. were first shortened; by 1.3, and the .13:

machine described by 3. A. Bradford, W. R. Harlan and' H. R. Hanmerin'lndustrial and Engineering Chemistry, vol. 28, pp. 836-9 (1936). Thesmoke which passed through the cigarettes was collected and analyzed forn cotine and tar content.

Control filters without a powdered additive were also prepared from thesame sellulose acetate tow containing the same amount ofdi(methoxyethyl) phthalateplasticizer. These filters were attached tothe same brand of standard king size cigarettes shortened by 13 mm.These cigarettes were also smoked to a total butt length of 35 mm. bymeans of the smoking machine. The smoke which passed through thecigarettes was collected and analyzed for nicotine and tar content.

- Ten unfiltered king size cigarettes (same brand) which were notshortened by 13 were smoked to a butt length of 35 mm. by means of thesmoking machine. The smoke which passed through the cigarettes wascollected and analyzed for nicotine and tar content.

' The results obtained from the three sets of cigarettes are listed inTable I.

Table I Average Pressure Drop, inches mg. Tare Found in the Smoke mg.Nicotine Found in Smoke Cigarettes without filters (85 mm.

length) Cigarettes with cellulose acetate filters- Cigarettes withcellulose acetate-magneslum carbonate filters Pressure drop is expressedabove in inches of water at an air flow rate of 17.5 cc./sec. throughthe cigarette.

EXAMPLE 2.CALCIUM CARBONATE The procedures described in Example 1 wererepeated using the same tow of cellulose acetate and the sameplasticizer but using in place of the magnesium carbonate a powderedcalcium carbonate (CaCO capable of passing through a 325-mesh screen.The treated tow contained 14% plasticizer and 20% calcium carbonate(based on the total weight of the treated tow) as it left the dustingchamber. The baked plugs were cut into 13 mm. filter tips and attachedto the standard king size cigarettes which had been shortened by 13 mm.These filtered cigarettes were smoked to a total butt length of 35 mm.on the smoking machine operated under the same conditions as in Example1, and the smoke which passed through the cigarettes was collected andanalyzed for nicotine and tar content.

The collected smoke contained 90 milligrams of tar and 13 milligrams ofnicotine. This corresponds to a reduction in tar of 44.6% and areduction in nicotine of 48.0% due to the filter. The cigarettes had anaverage pressure drop of 4.3 inches of water.

EXAMPLE 3.-CALCIUM CARBONATE The procedures described in Example 1 wererepeated using a tow of cellulose acetate yarn containing 5,000

filaments of 16 denierper filament, a. plasticizer consist-' The treatedtow contained 60% cellulose acetate, 30%

calcium carbonate, and 10% plasticizer. A control tow of celluloseacetate yarn of 5,000 filaments, 16 denier per filament, and containing14% triethyl citrate, was.

also prepared. Both treated tow samples were processed into filter rodsand the rods were heated at 60 C. for one hour. Filter tips of 13 mm. inlength were prepared from both sets of rods and placed on the standardking size cigarettes which had been shortened by 13 mm. Ten cigarettescontaining the calcium carbonate filters and 10 cigarettes containingthe control filters were smoked to butt lengths of 35 mm. on the smokingmachine. The smoke which passed through the cigarettes was collected andanalyzed for nicotine and tar content. a

From the values listed above and in Example 1 it can be seen that thefilter containing the combination of acetate fibers and calciumcarbonate reduced the amount of tars collected by 29.4% and the amountof nicotine collected by 28.0%. The control filter reduced the amount oftars collected by 4.9% and the amount of nicotine collected by 4.0%. Theincrease in pressure drop of the filtered cigarette due to the additionof the calcium car bonate to the filter was only about 5%.

EXAMPLE 4.- CALCIUM CARBONATE A tow of regenerated cellulose yarn(viscose) containing 16,000 filaments of 6 denier per filament wasspread out to a width of 10 inches and sprayed with a 25% aqueoussolution of dextrin glue. While the tow was still spread out and wetwith the glue it was passed through a dusting chamber where itrwasuniformly covered with a fine calcium carbonate dust of 0.1 micron'particle size (Multifex MM). On leaving the dusting chamber the towconsisted of 40 parts regenerated cellulose fibers, 30 parts glue (25solution) and 30 parts calcium carbonate. The combination was pulledback into the form of a compact bundle or cord and fed into a filter-rodmaking machine which paper wrapped it and cut it into filter plugs 78mm. in length and 7.5 mm. in diameter. The rods were heated for 1 hourat 100 C. to dry the glue and bond the powder to the fibers. The plugswere then cut into l3-mm. filter tip lengths and attached to mm.standard king size cigarettes which had been shortened by 13 mm. Ten ofthese cigarettes were smoked to a total butt length of 35 mm. on thesmoking machine. The smoke which passed through the cigarettes wascollected and analyzed for nicotine calcium carbonate, was prepared in asimilar manner. The plugs from this tow were heated for 1 hour at C. andcut into filter tips 13 mm. in length. These tips were attached to'85mm. standard king size cigarettes which had been shortened by 13 mm. Tenof these cigarettes were smoked to a total butt length ,of

animu passed hrough. the cigarettes was collected and analyzed;

' fornicotinh and tar content'.-

Arerage mg. Tats mg; I Pressure Found in Nicotine rop, the Foundininches Smoke I 'the V I Smoke Clgaretteswith the'regenera'ted fllter' li (85 mm. length) Y 4:1 j 140' i 21 lose-CaOO; filter (85 mm.'length)..I I

From the. values listed above and in Example 1 it can' be seen that thefilter containing the combination ofregen eratcjd, cellulose fibersandcalciurn carbonate-reduced the amount of tars collected by. 38.7% andthe amount of nicotine collected by 36.0%. The control filter or re-'generated cellulose fibers reduced the amount oi tars collectedby 14.1%and the amount of nicotine collected by' ..-Q%-, Th incr asclin thcp ssnrc 4:92.52! t e filtered cigarette due to the addition of the calciumcarbonateto thfe'filter-was only about 5%.

EXAMPLE 5.=CALCIUM CARBONATE .A towof cellulose acetate yarncontaining...12,090

1 Pressure dro in inches or water at an an new rate 0117.5 e seclinathrough the cigarette. I V From the results listed above; it can be seenthat the filter containing the combination of cellulose acetate fibersand calcium carbonatere'duced theamonnt of tars collected by 44%; andthe amount of nicotine collected by- 48%. cellulose acetate fibers hutnocalcium carbonate reduced the amount oftarsby only 2.1% andthe. amountof nicotine by althoughits averagefpressiire'drop was filaments; of 5denier perfilamentwas, spread to a widtlr of'lZinches and'sprayedwith-anemulsioiiconsisting (by weight) of 0.03 part7 sodium lauryl siilfate; Ipart di(methoxyethyllphthalatc. plasticizen. 2 parts water,. and 3 partscalcium carbonate powder of ultimate particle size of approximatelyomicrons. The spread tow was then pulled baclc into acompactbundle orcord and fed into, a cigarette-filter plug. making machinewhich paperwrapped it and cut it intofilter rods 18 in equal to that of thecellulose acetate-calcium carbonate filter.

EXAMPLE A. 1 'UM. CARBQNATE A tow O f cellulose acetate yarn containing14,000

filaments 6f 5 denier per filament wasspread to a width of 12 inches andsprayed with a suspension of 51% calcium carbonate powder indi(mcthoxyethyl)- phthalate plasticizer containing 33% ethyl alcohol.The calcium carbonate powder hadan ultimate" particl'size of 3microns.

The spread tow was pulledbaclc;intoa'compact bundle at cord and fed intoa cigarette finer magmatlength and, 8 11am. in diameter. Therodswerheated;

for minutes at 100 C. to evaporate. the water and to. bond the calciumcarbonate firmly to. the fibers by.

means of theplasticizer'. Analyses of the plugs: ihdi'-' cated thatthey, consisted-of 51% cellulose acetate fibers,

33% calcium carbonate, 5% moisture; and 11% di- (methoxyethyljphthalate'plasticizer. The heated and cooled plugs were quite firm and the calciumcarbonate was firmly bonded tothe fibers. The plugs were cut into13-min. filter tiplcngthsaand attached tdstand'ar'd American king; size:(85 mm.) ci'garette's which had been shortened by 13 mm. Thesefiltered':cigarettes were smoked to a total butt length of 35 mmton'the standardsmoking. machine described in Example 1. The smoke whichpassedthrough-the cigarettes wasv collected and,

analyzed for nicotine and tar content.

A tow. of ccllulose'acetate yarntcontaining 20;000.' fila ments' of 5.-denier per filament was spread to a'width of =11 inches and sprayed withan emulsion consisting:

of20l03; part sodium lauryl sulfate; 1 part di(metlioxy--ethyl)phthalatei plasticizer; and 2 parts water. tow, containingnocal'cium carbonate, was converted into filter plugs in the. mannerdescribed above and the plugs were dried for thirty' minutes. at 100";C. Analysesof these plugsindicated that they consisted of 84% cellulose.acetate fibers, 12% difmethoxyethyhphthalate plasticizer, and 4%-moisture. The'plugs were cut' into- I3- mm. filter tips and attachedv toten standard king size cigarettes shortened by l34 mm." Thesecigarettes. were also. smokedto.totalbuttlenghts of'35 mm.onithersrnoking machine, The smoke which passed. through: thecigarettes? was! collected and: analyzed for nicotineand tar content.

Ten unfiltered? standard kingsize cigarettcsg which not shorteneduby 13'mm. were smokedto a butt length of 35' mm. by'rneansof the smokingmachine. Thesmoke which passed through the: cigarettes'was col.- lectedand analyzed for? nicotine andjtaiicontent; Thea'results. obtained fromthe three sets ofi cigarettes: ars-listerhinflfableelk.

s i lfi i cl fiinf i Wfifii t iid cu it fl t fil rods 78 .in length and8 mlu iil'diamle'tcie Th erode wereheated for thirty minutes at C.to'evaporate the ethyl alcohol and bond the. calcium carbonate powder tothe fibe'isby means of'the plasticizer.- Analy; ses ot the" plugs;indicatd that they c'ons'is'ted of 6 5 cellulose acetate fibers, 20calcium carbonate powder,

and*l3% plasticizer; The heated andcooIed- Iugs were.

quite and the calcium carbanatswagam bonded to the fibers.

rettes which had been sho'r't'e'ned 13f mm. These filtered cigaretteswere smoked to'a total'buttlength of 35 mm. on the-standard smokingmachine described in Example The smoke which passed-through thecigarettes was collected and analyzed for nicotine andtar content-- I VII I II I The collectedsmokecontained lll mgxof taif and 15 mg. ofn'icotine. This corresponds to a reduction-in tar 0t 33'%""and areduction in nicotine-of 40%" due to 'th'e filter when the, valuesobtained are compared withthe' unfiltered cigarette values listed inExarnple 5; The filtered cigarettes had an average'pres'sure drop; of 43inches ofwater.

EXAMPLE CARBON-ATE A tow otjcellulose acetate yarn containing14,000'fila-1 ments of 5 denier per filament was spread to E Wldfli' of12.. inches and sprayed with a suspension of*58% calcium carbonatepowder in glycerol tripropionate ::plasticizer. The calciumcarbonate'po'wder had an ulti mate particle size-between 7 andl0-"microns'.

The spread tow'wvas pulled back" into a compact bundle or cord and fedinto a cigarette filter plug ma'king? machine which pape'r wrapped itand cut it into filter 'rods 78 mm. in length, and'8: in diameter;

Within one hour at room temperature the .rods were rigid and thecalciu'rit carbonate'wasfirmly bonded to theifibers. The plugs were cutinto 13 mm. filter tips and attached to standard: king size;cigarettes-which; had-been hort- 175,; eneni by 'lheae filteredtcisarees weresrnoked The filter containing the larger number of I The'plugfsfwere cut into filter tips and attached to standard Americafi'king size'digzi:

EXAMPLE 8.MAGNESIUM PHOSPHATE 3( 4)2] A row of the type employed inExample 1 was treated as described in that example with magnesiumphosphate (325 mesh) rather than magnesium carbonate as employed inExample 1. On leaving the dusting chamber, the tow of fibers contained14% plasticizer and 18% magnesium phosphate based on the total weight ofthe combination. Filters were made from this treated tow and fastened tocigarettes which were then test smoked, all by methods as described inExample 1. Analytical data obtained showed that cigarettes withcellulose acetate-magnesium phosphate filters (85 mm. length) had anaverage pressure drop of 4.2 inches. The smoke contained 98 mg. of tarsand 15 mg. nicotine. Comparison of this data with the data obtained forcontroled filters and unifiltered cigarettes in Example 1 shows that themagnesium phosphate filter reduced the amount of tars collected by 40.0%and the amount of nicotine by 40.0%. The increase in pressure drop ofthe filtered cigarettes due to the addition of the magne-..

sium phosphate to the fiber was only about EXAMPLE 9.-CALCIUM PHOSPHATECa (PO capable of passing through a 325-mesh screen in the dustingchamber. The tow of fibers prepared in this case contained 14%plasticizer and 20% calcium phosphate (based on the total weight) as itleft the dusting chamber. The baked plugs were cut into 13-min. filtertips and attached to the standard king size cigarettes which had beenshortened by 13 mm. These filtered cigarettes were smoked to a totalbutt length of mm. on the smoking machine and the smoke which passedthrough the cigarettes was collected and analysed for nicotine and tarcontent.

The collected smoke contained 100 milligrams of tar and 16 milligrams ofnicotine. This corresponds to a reduction in tar of 38.6% and areduction in nicotine of 36.1% due to the filter. The cigarettes had anaverage pressure drop of 4.4 inches of water.

0 EXAMPLE lO.--CALCIUM PYROPHQSPHATE i z a 'zl The procedures describedin Example 1 were repeated using a tow of cellulose acetate yarncontaining 5,000 filaments of 16 denier per filament, a plasticizerconsisting of triethyl citrate, and a powder consisting of calciumpyrophosphate, Ca P O capable of passing through a 325- mesh screen. Thetreated tow contained 60% cellulose acetate, 30% calcium salt, and 10%plasticizer. A control tow of cellulose acetate yarn of 5,000 filaments,16 denier per filament, and containing 14% triethyl citrate, was alsoprepared. Both treated tow samples were processed into filter rods andthe rods were heated at 60 C. for one hour. Filter tips of 13 mm. inlength were prepared from both sets of rods and placed on the standardking size cigarettes which had been shortened by 13 mm. Ten cigaretescontaining the calcium pyrophosphate filters and 10 cigarettescontaining the control filters were I0 smoked to butt lengths of 3 5 mm.on the smoking machine. The smoke which passed through the cigaretteswas collected and analyzed for nicotine and tar content. Results were asshown in Table III.

Table III Average mg. Tars mg. Pressure Foundln Nicotine Drop, a Foundininches Smoke the Smoke Cigarettes with cellulose acetate filter mm.lengt 3. 8 155 24 Cigarettes with cellulose acetate- Coal-50 filter (85mm. length) 4. 2 17 From the values listed above and in Example 1, itcan be seen that the filter containing the combination of acetate fibersand calcium pyrophosphate reduced the amount of tars collected by 32.6%and the amount of nicotine collected by 32.0%. The control filtersreduced the amount of tars collected by 4.9% and the amount of nicotinecollected by 4.0%. The increase in pressure drop of the filteredcigarette due to the addition of the calcium pyrophosphate to the filterwas only about 5%.

EXAMPLE 11.CALCIUM DIPHOSPHAT A tow as described in Example 4 wastreated and converted into filters as described in that example, exceptthat calcium diphosphate (capable of passing through a 325 mesh screen)was used in place of the calcium carbonate. Rods were made and tested inthe same way. They contained 45 parts regenerated cellulose fibers, 30parts glue (25% solution) and 30 parts CaHPO powder. The filters wereevaluated by test smoking as conducted in Example 4 and comparison tocontrol filters and unfiltered. cigarettes as tested in that example.The filters containing the calcium acid phosphate had an averagepressure drop of 4.3 inches. and their smoke contained 102 mg. tar and16 mg. nicotine.

From the values listed above and in Example 1, it can the filteredcigarette due to the addition of the calcium 7 acid phosphate to thefilter was only about 5% In carrying out the operation of thisinvention, the

purity of the carbonate or phosphate employed is not a critical factor.Rather, the form of its particles is more important. The salt should bein a finely powdered form so that it can be readily slurried in a liquidor passed through a spraying nozzle. While the exact size of theparticle does not appear to be critical, it is indicated that the saltadditive should be at least capable of passing through a 200 meshscreen. Commercial grades of the salts of the invention generally may beobtained in a particle size which will pass through a 325 mesh screen.Advantageously, a salt is used which has at least 80% of its particlesof a diameter less than the diameter of the fibers of the filter. Forfibers of the size used in the example above, no substantial number ofparticles should 7 be as large as twice the filament diameter or assmall as one-tenth the filament diameter although these limits may nessof the invention extends to other fibrous filters, in-

= r dissoliied 6r plastic material iii'eontigtiofis filament v t aregenera'uy dr'ie'nted lengthwi'se of the filter element ver fies'sjeenrto derive special benefits item the chem at -(2) That where theadditive is to whe'r'eby the particles;

surface or superficial su ace' wi V v covered. Itj'isi also most asily;acQOmplished whenthe pb 'srcs v sre e :n rtieu a y-whereit e fibers arewith the body of the filter j It; is preferred to' use forfilter;

I preparation in 'accor'danceqwithtthe present invention a continuousstrand, e.g. 3,000 to 35,000 filaments, the filaments being of 16' t6 3'deifieri aid having areiir 4 to '10 crimps per; inch, 7

' iQIiPiiIG insubstantial longitudinalalignment and are coextensive v12.; A tobacco s fioke filter eiemeateemprisiagssufidie, of" continuous'eiimped cellulose-acetate filaments, a content comprising droplets ofplas'tieizer for the fila V-me'nts on said filaments whereby thecio'ntiinitii cellir" i lbselacetatel filaments are bonded to oneanother at ;By the 'eripressiont fsiii'face solvation as used herein isr V powdered salts to the filaments; the powdered sans being meant thecreation; by the action of a solvent or plastigizerand/ or heat,ofsanadhesivmtacky ortreadily bond tion of surface portions of mat I, Ithere is produced a welding adhesion betweetiedja ea e at wea ers wfilamfit and e tae aaiens wi ifidw iiito or time with similar 'porti nse sol atioifhonds between fibersare sometime; d to as fusedorffweldedlbonds. y I;

the present S It i to he, no ed that while the filters of pronerties andbehayior of the wafer ins'oluble' inorganic salt additives; yet theinvention'appears to be equally dependeiit 1115611 the s tructuralcharacter of the filter. In this regard, the more important structuralfactors found in the advantageous form of;- the inyention seem to be:

' I) That me aligned arrears be riiido'mly at fanddnily spaeediriterals. This may be ac ed by tion' before the fibers are spun. L A ,7 fiPii i df fif a with afiberbonding agent; In other words, no material:

Obviously" no 315 eizefshoulr ljbe'; emplbysea win a detfiiiientalaetiono'n'the'salt particles? (3')"' That'substan ally errat 51; 'pa rticles'be a off the surfaces ofthe' filenients, supfiort'ed ments, andsubstantially immobile with respect thereto. This structure is bestaccomplished by softeniiigof portic'ins of the-filament surf sf withasolvent'of by eer e; atin'g a superficial surfac with a \film formihgmaterial be slightly" embedded, in the t Hein'gfedatedi or:

diameters"- of the particles are not too different from the diameters ofthe filaments, the major portibnof' the particles being for instance,le'ssi than'twicfe the filament erallyioriejnted lengthwiseo'fthefilterelement andiextexidf from endftdend of'th e terel'eiii'enJa' cofitent of plas'tb' ciz'e'r for. the filaments on said filaments; avliereb'jf the 7 continuous erirnne d' fil'anients'afe bonded td-oiieOtlieratr'andcEm points of ccintacft and a content ofi a water-insolublesalt powder from the group consistingof-icalcium andt magnesium; saltscarried on and by: the continuousfilaments,- said plasticizer alsosewing to: bond-"saidmowdere'd salttmthefilamentsa;

- ing condition of the filaments by solution orincipient solual wherebyrandom rioints' ofcontact' and a content er atpowdered salt from thegroup consisting-of calcium" and magnesium salts carried on and by thecontinuous, cellulose acetate filaments; the aforesaid 'plasticizer s ering to bond said characterized in that at least 80% of the particlesthereof have a diameter less than the diameter of thecontinuouscellulose aeetatefilaniiits" 5nd ie substantial number of the powderedsalt partic es beiii as large as twice the filament diameter or slam asone-rawhide filament or continuous campedcarna e; aeaae filamenfsl'whicharid-extend fin i end to and 6f the filter elemenga con tent offilalsticizr the group consisting oi phthalates citr t es} andfiropio'nates carried on said filaiii'ents whr'e by the eehti nouscellulose acetate filaments are In tit-one gridthe'r at randpni paintserenfat andja of sanj from the glOilfl consisting of phosphate malc'iuni and magnesimi'csmed on and by alasalts being male eraiaowdersmaller tieize'r serving to beiidsaid 5 of saunas-unheatedsyfimeaqfilaments, tm'dr'f 10% of a bonding material eofnp'atible with the'filameiits icarried Qnjthe filamentsfastdtoplets whereby the filaments'are bonded at randomgoints without coating of the filainppwdered formfrom hibl emit er sitar-Tire dionyaii'dflby said filaments, said 1; "d-

ndingithe' salt powdef 'to the fiiarherit's em; is attained.

pfo

' maa siodo'edarmuduswarpe eellulosefacetate' mamas 4 of'iidt statesman8 denierigerfiIameht which are nrau briemed lengthwise o'fthe filterelementand 7 train end nd o f th'filtje element at least 10% plasticiierfr 1a the rdti onsistia or path -integ a rates; and p fiioiiates earriedby said iilamhts at least 26% Qfr were i ia' sr fi @9 1 thepowderedsaltis fromthe group consisting of calcium v and magnesium carbonate;magnesium carbonate. calcium phosphate! magnesium phosphate, 7 ealeiumpyro pho sphate mag ies ium pyrophosphatq calcium, metaphosphate andmagnesium' 'met-aphos ihate;

about: 8 crimpsper inch, said-filaments carrying. dropletsofiaplasticizer fromthe group consisting of phthalates;t1citrates,-and'propionates,said plasticiaer being present on thefilaments in an amount-greater than 1 0-% by weight whereby; thefilaments are-bonded to each other atram dom;points 'ofcontact and thepl-asticized filaments carry on their; surface at least- 20% by weightot a powdered 1 'water'insoluble salt from-the group consisting of,calcium 6: A tobacc'o'smoke filter element onipr'ised (it more.

is water insoliible calcium and magnesium salts" carried on s. A filterelement consisting 'ofa bundle; dentist's:- acetate; continuous crimpedfilaments hav ng at least 9. A tobacco smoke filter element comprising abundle of continuous crimped synthetic filaments, more than 10% of aplasticizer as a bonding medium carried on the filaments in dispersedform whereby the filaments are bonded at random points, more than 10% ofa salt in finely divided form from the group consisting of waterinsoluble calcium and magnesium salts carried on and by said filaments,said plasticizer also assisting in the bonding of the aforementionedfinely divided salts to the filaments whereby an improved filter elementis obtained.

10. A tobacco smoke filter element comprising a bundle of continuouscrimped cellulose acetate filaments which are generally orientedlengthwise of the filter element and extend from end to end of thefilter element, a content of plasticizer for cellulose acetate containedin the filaments whereby the continuous cellulose acetate filaments arebonded to one another at random points of contact, and a content of afinely divided salt from the group consisting of phosphates andcarbonates of calcium and magnesium carried on and by the filamentswhereby an improved filter element is obtained.

References Cited in the file of this patent UNITED STATES PATENTS656,649 Landfried Aug. 28, 1900 1,127,771 Jones Feb. 9, 1915 1,784,566Andrews Dec. 9, 1930 1,936,999 Teague Nov. 28, 1933 1,950,542 CopellMar. 13, 1934 2,181,614 Striefling Nov. 28, 1939 2,301,159 Drechsel Nov.3, 1942 2,789,563 Taylor et al Apr. 23, 1957 2,780,228 Touey Feb. 5,1957 2,805,671 Hackney et a1 Sept. 10, 1957 2,832,351 Hale Apr. 29, 1958FOREIGN PATENTS 813,324 France Feb. 22, 1937

1. A TOBACCO SMOKE FILTER ELEMENT COMPRISING A BUNDLE OF CONTINUOUSCRIMPED CELLULOSIC FILAMENTS WHICH ARE GEN-